Influence of phase-sensitive interaction on the decoherence process in molecular systems

The character of the interaction between an impurity vibrational mode and a heat bath leads to certain peculiarities in the relaxational dynamics of the excited states. We derive a non-Markovian equation of motion for the reduced density matrix of this system which is valid for initial, intermediate and kinetic stages of the relaxation. The linear phase-sensitive character of the interaction ensures the ultrafast disappearance of the quantum interference of the initially superpositional state and the effect of classical squeezing of the initially coherent state. On the other hand, the second power interaction induces a partial conservation of the quantum interference.